Articular cartilage is a complex structure that, once damaged, has little capacity for permanent repair. The problem lies in the inability of the body to regenerate tissue with the appropriate macromolecular constituents and architecture of normal hyaline cartilage. Although full-thickness defects are capable of stimulating a repair response, the resulting scar tissue or fibrocartilage is inferior and cannot withstand long-term, repetitive use.
To date, no technique has been completely successful in achieving normal degenerative articular cartilage. Arthroscopic lavage and debridement provides temporary relief of symptoms by removing degradative enzymes that contribute to synovitis, but it also leads to the further breakdown of articular cartilage. Bone marrow stimulation techniques such as abrasion arthroplasty, drilling, and microfracture produce only fibrocartilage, and therefore, do not offer a long-term cure. Perichondral and periosteal interposition grafts produce repair tissue that is similar to hyaline cartilage in some respects, but lack its mechanical durability. Like bone marrow stimulation techniques, interposition grafts introduce precursor cells, which have a tendency to differentiate along lines other than cartilage. This leads to an inferior quality of repair tissue.
One technique that provides repair with living hyaline cartilage is osteochondral autograft transplantation, also known as mosaicplasty. This procedure involves removing injured tissue from the damaged area and drilling one or more sockets in the underlying bone. A cylindrical plug graft, consisting of healthy cartilage from the knee is then implanted in each socket. Commercially available instruments for use in this procedure include, Acufex, manufactured by Smith and Nephew, Inc., Andover Mass., COR System, manufactured by Innovasive Technologies, Marlborough Mass., and Arthrex Osteochondral Autograft Transfer System, manufactured by Arthrex, Naples, Fla.
The disadvantages of the current techniques, which harvest cylindrical cores from the knee as grafts, include donor site morbidity, a limited size and supply of grafts, dead space between circular grafts, graft integration and the different mechanical properties and geometry between donor and recipient hyaline cartilage.